Liothyronine in Children With Single Ventricle Congenital Cardiac Malformations Undergoing the Fontan Procedure

OBJECTIVES: I. Determine the pharmacokinetics of exogenous liothyronine administered in children undergoing the modified Fontan procedure.

II. Determine the liothyronine supplementation dose that counters the fall in serum liothyronine concentrations and provides the greatest potential myocardial benefit after the modified Fontan procedure.

III. Evaluate the potential toxicity of exogenous liothyronine administered in children undergoing a modified Fontan procedure.

PROTOCOL OUTLINE: This is a randomized, placebo controlled, dose escalation study.

Initially, patients are randomized to receive either 1 of 3 different dosages of liothyronine or placebo after undergoing the Fontan procedure. If no unacceptable toxicity is observed in this group, a third dose level of liothyronine is added to the randomization. A total of 7 patients are enrolled at each dose level. All randomized study drugs are administered by continuous infusion over 1 hour after surgery.

Cardiac function is assessed 5 days after surgery.

• Single ventricle congenital cardiac malformation
• Must undergo modified Fontan procedure
• No concurrent medications known to interfere with thyroid metabolism including propranolol and amiodarone
• No hepatic dysfunction
• No renal dysfunction
• No pre-existing thyroid dysfunction